When would you expect to hear a grinding noise in a five speed transmission?

Hearing a grinding noise in a five-speed transmission typically indicates that the gears are not properly engaging with one another, which often happens when shifting gears. This grinding sound occurs because the gear teeth are clashing rather than smoothly meshing together.

This scenario can be attributed to several factors related to the shifting process itself, such as improper technique, worn or damaged synchronizers, or insufficient lubrication. When the clutch is not fully disengaging, it results in the gear not stopping completely before attempting to shift, leading to that unwanted grinding noise.

While the other situations present their own concerns, they do not typically directly result in the grinding noise associated with gear shifting. For instance, changing the fluids should not produce grinding noises if performed correctly, and having the engine off would generally prevent the gears from turning, implying that no grinding should occur. Not fully depressing the clutch can lead to grinding, but it is considered part of the shifting action, essentially reinforcing why option C is the most direct cause of a grinding noise in this context.